1. Technical Field
Exemplary embodiments of the present disclosure generally relate to an image forming apparatus such as a copier, a facsimile machine, or a printer, and a process cartridge detachably attached with respect to the image forming apparatus.
2. Description of the Related Art
In conventional electrophotographic image forming apparatuses, after a toner image is transferred to an intermediate transfer body or a transfer sheet, an unnecessary transfer residue toner adhering to a surface of an image carrier such as a photoreceptor serving as a cleaning target member is removed by a cleaning device serving as a cleaning mechanism. A configuration of a cleaning member of the cleaning device is typically simple. From a point of good cleaning performance, employing a strip shaped cleaning blade is well known. The strip shaped cleaning blade is formed of a strip shaped elastic body such as polyurethane rubber. A base end of the strip shaped cleaning blade is supported by a supporting member and a leading-edge ridge line portion of the strip shaped cleaning blade is pressed against an outer circumferential surface of the image carrier from a direction counter to a direction of movement of the outer circumferential surface of the image carrier. The transfer residue toner on surface of the image carrier is removed by stopping and scraping off with the strip shaped cleaning blade.
To respond to a demand of high image quality of recent years, employing an image forming apparatus using a toner (hereinafter referred to as polymerized toner) having a small particle diameter and a shape close to a sphere formed by, for example, a polymerization method is well known. The polymerized toner has a high transfer efficiency compared to a conventional pulverized toner and meeting the above-described demand is possible. However, sufficient removal of the polymerized toner from the surface of the image carrier with the strip shaped cleaning blade is difficult and a problem of cleaning failure is generated. The generation of cleaning failure is due to the polymerized toner having the small particle diameter and a good spheroidicity slipping through a slight space formed between the strip shaped cleaning blade and the surface of the image carrier.
To suppress slipping through of the polymerized toner, there is a need to enhance a contact pressure between the strip shaped cleaning blade and the surface of the image carrier and enhance cleaning performance cleaning blade. However, as shown in FIG. 7A, when the contact pressure is enhanced, a friction force between a conventional cleaning blade 262 and a surface of an image carrier 23 is enhanced and the conventional cleaning blade 262 is drawn towards a moving direction of the image carrier 23 indicated by arrow D in FIG. 7A. Accordingly, curling of a leading-edge ridge line portion 262c of the conventional cleaning blade 262 occurs. The conventional cleaning blade 262 may generate an abnormal sound due trying to return to an original state of the conventional cleaning blade 262 in resistance to curling. Repetition of curling and returning to the original state generates a chattering vibration. In addition, as shown in FIG. 7B, when cleaning is continued in a state in which the leading-edge ridge line portion 262c of the conventional cleaning blade 262 is curled, local wear is generated at a point a few μm away from the leading-edge ridge line portion 262c on a leading-edge surface 262a extending from the leading-edge ridge line portion 262c in a direction of thickness of the conventional cleaning blade 262. When cleaning is further continued with the above-described state, local wear becomes large and eventually the leading-edge ridge line portion 262c and a vicinity of the leading-edge ridge line portion 262c including a part of the leading-edge surface 262a and a part of an opposing surface 262b is lost as shown in FIG. 7C. When the leading-edge ridge line portion 262c is lost, normal cleaning of the polymerized toner is not possible and cleaning failure is generated.
JP-2009-300754-A describes an image forming apparatus including a cleaning blade including a surface layer provided on an opposing surface opposite a surface of an image carrier in which a layer thickness becomes thicker as a distance from a leading-edge ridge line portion of the cleaning blade increases in a direction at a downstream side of a movement of the surface of the image carrier. In the image forming apparatus described in JP-2009-300754-A, an elastic blade of the cleaning blade contacts the surface of the image carrier with an initial contact width between the cleaning blade and the surface of the image carrier in a range from 30 μm or more to 80 μm or less. In addition, the image forming apparatus described in JP-2009-300754-A includes a lubricant coating device to coat a lubricant on the surface of the image carrier. By coating the lubricant on the surface of the image carrier, friction coefficient between the cleaning blade and the surface of the image carrier is decreased.
By providing the surface layer that is harder than the elastic blade on the opposing surface of the elastic blade, rigidity in the direction of the movement of the surface of the image carrier may be enhanced and curling of the leading-edge ridge line portion may be suppressed. In addition, by making the layer thickness of the surface layer become thicker as the distance from the leading-edge ridge line portion of the cleaning blade increases, the vicinity of the leading-edge ridge line portion is suppressed from becoming too rigid due to the surface layer. Accordingly, the leading-edge ridge line portion follows fluctuation such as decentering of a normal line direction of the surface of the image carrier and good cleanability is obtained. By making the initial contact width 30 μm or more, the contact pressure between the leading-edge ridge line portion of the cleaning blade and the image carrier is suppressed from becoming high and friction force between the leading-edge ridge line portion of the cleaning blade and the image carrier is suppressed from becoming high. As a result, force of drawing in the leading-edge ridge line portion of the cleaning blade in the direction of the movement of the surface of the image carrier is suppressed from becoming strong and curling of the leading-edge ridge line portion is suppressed. Further, by making the initial contact width 80 μm or less, reaching a wear width at an early stage in which cleaning failure is generated is suppressed.
However, in recent years, a further long operation life of the cleaning blade is desired and narrowing the initial contact width is needed. The narrower the initial contact width is, a time to reach the wear width in which cleaning failure is generated becomes longer and a longer operation life of the cleaning blade may be obtained.